1. Field of the Invention:
The present invention relates to a method of detecting a defective portion, such as a portion unfilled with a cement intimate mixture in a region filled with the cement intimate mixture such as cement or mortar, or a peeled and separate portion of the cement intimate mixture in a building or structure. More particularly, the present invention relates to a method of detecting a defective portion easily, rapidly and without fail by utilizing a phenomenon in which the attenuation characteristic of a tapping sound generated by tapping the cement intimate mixture portion of the building from the outside differs depending on the presence or absence of the defects.
2. Prior Art:
The present invention is applicable, in a building having a tile on the structural surface of the building interposing a mortar filled portion therebetween, to detect a peeled position between the mortar portion and the structural surface, or between the mortar portion and the tile.
The present invention is, also, applicable in a building having a mortar coated on the structural surface of the building, to detect a peeled position between the inner surface of the mortar and the structural surface of the building.
Furthermore, the present invention is applicable in a concrete building to detect an unfilled position in a concrete filled portion inside of the structure of the building.
The following methods are known in the art as methods for detecting a defective position in a cement intimate mixture in a building or structure.
1. A method of detection based on the magnitude of an echo generated by tapping or striking a finished surface, disclosed in Japanese Patent Laid-Open Publication No. 60-211360 (1985).
2. A method of detection based on the characteristic of a waveform of an echo generated by tapping or striking a finished surface, disclosed in Japanese Patent Laid-Open Publication No. 61-161449 (1986)
3. A method of detection based on the repulsion acceleration generated in a tapping tool by tapping a finished surface, disclosed in Japanese Patent Laid-Open Publication No. 61-292554 (1986).
4. A method of detection utilizing an infrared ray.
5. A method of detection utilizing a ultrasonic wave, disclosed in Japanese Patent Laid-Open Publication No. 57-136160 (1982).
However, these prior art methods are not problem free. Specifically, in each method of references 1, 3 and 5 (above), the depth of a defective position from the surface of the building is limited to about 20 mm, and the detection accuracy is degraded when the depth increases more than that. In the prior art methods of references 1, 2 and 3, when a defect of peeling of mortar or the like is present in a deep portion it is difficult to be detected satisfactorily, for example, where in the case of an outer wall of a building, substrate mortar has been peeled off the structural surface of the building, or the mortar has not been filled from the first. As a result, if this condition is left as it is, the peeling of the mortar will be increased, and there is the danger that a large area of mortar filled portion will fall on the ground.
Furthermore, in the prior art method of reference 5, in order to detect an unfilled or peeled position in a deep portion, the building body must be sandwiched with a receiver and a transmitter, respectively, at the front and rear sides thereof. Thus, the positioning of the receiver and transmitter is difficult, and it is impossible to operate for detection by a single operator.
On the other hand, in the prior art method of reference 2, in order to process and analyze the tapping sounds, it takes 500 ms for each sound signal. In the prior art methods of references 4 and 5, the apparatus is complicated and the manipulation thereof is difficult, and it requires technical knowledge and experience.